Sulfonated ionomers, specifically sulfonated EPDM and lightly sulfonated polystyrene are materials that have been disclosed in previously filed U.S. patent applications and issued U.S. patents. When sulfonated to levels of about 1 mole percent (that is, from 10 milliequivalents per 100 grams of polymer up to 50 milliequivalent per 100 grams of polymer), these materials display a strong ionic crosslinking. The manifestations of this strong ionic crosslinking are that the elastomers appear to be covalently crosslinked, but in fact can be dissolved in suitable solvent systems. The instant invention differs from the above systems in that, it describes the sulfonated ionomers in blends with unsulfonated polymers which are extended by suitable solvents or oils to yield systems which are not dilute solutions, and which display very high viscosities and simultaneously display a high degree of creep behavior.
Several applications and issued patents which have described the dilute solution behavior of sulfonated ionomers disclose how sulfonation can be employed to critically control the viscosity of both lubricated compositions and organic fluids. Similarly the use of sulfonated EPDM in oil extended formulations containing up to 100 or 150 parts of oil per 100 of elastomer are well known and are described in several U.S. applications. The use of sulfonated EPDM in asphalt compositions have also previously been described. The blend compositions of sulfonated and unsulfonated polymers in their bulk state has been disclosed in previous U.S. applications, but none of these aforementioned applications are relevant to the instant invention. The instant invention teaches highly extended hydrocarbon oil blends of sulfonated ionomers and their unsulfonated counterparts which display unusual viscoelastic behavior summarized as follows: (a) at high strain rates the material behaves as if it were covalently crosslinked, (b) at very low strain rates behaves as if it were a simple viscous fluid, and (c) at comparable concentrations the blends have a more persistent network than the sulfonated ionomer gels alone or the solutions of unsulfonated polymers.
The compositions described in this invention, therefore, differ from previous disclosures in U.S. patent applications and issued U.S. patents for the reasons that previous disclosures such as those dealing with oil extended rubber claimed a very high degree of ionic crosslinking and a very low extension with a suitable fluid; for example, in sulfonated EPDM systems extension with oil up to 150 parts per hundred of polymer were widely disclosed and claimed. This invention differs from that previously described compositions in that (i) the levels of oil typically employed with sulfonated EPDM in the instant invention are nearly an order of magnitude higher and (ii) the present invention deals with a blend system of sulfonated and unsulfonated polymer. Accordingly, in the present invention over all there is a much lower level of ionic crosslinking which is an integral part of the instant invention. Previous disclosures have also described very dilute solutions in oil of sulfonated ionomers. Such cases are different from the present because (i) in these cases most often a polar cosolvent was used and (ii) the systems were normally true solutions, i.e., being Newtonian in nature. Other disclosures based on the blends of sulfonated and unsulfonated polymers are different because (i) such blends were prepared in true bulk state with the aim of using them in their bulk state and (ii) the blending of the polymers was done using a typical plastic processing unit such as the mill roll, extruder, etc.
The compositions of this invention are neither of the above in that the composition of the instant invention displays a high degree of ionic association or entanglement when stressed at rapid rates, but yet which, when subjected to stress over long periods of time, will slowly creep and flow. This behavior is often observed with very high molecular weight polymer materials having certain types of relaxation times. Usually high molecular weight polymers that exhibit such behavior are in their bulk state, however, the composition of this invention appears to differ significantly from conventional polymeric materials in the scope and perspective of the relaxation times involved.